Regulatory agencies around the world have recently promulgated regulations strictly limiting the emission levels of internal combustion engines and, in particular, diesel engines that power various equipment such as electrical generators. These regulations have required manufacturers of engines and power generation equipment to use aftertreatment systems as an add-on to their power systems. For example, U.S. Pat. No. 7,221,061 B2 to Alger, et al., issued May 22, 2007 and incorporated herein by reference, discusses a power generating system having an aftertreatment system (process module) mounted to the exterior of a power generation system, as reproduced in FIG. 1 hereto. Such aftertreatment systems reduce the levels of emissions produced by the power generation systems and allow them to comply with applicable regulations.
The elements of an engine aftertreatment system are selected dependent upon: (i) the regulations in the region in which the system is to be used; (ii) the type of power source in the power system; and (iii) the application of the equipment, such as power equipment or power generation. For example, if the power source uses diesel fuel, some regulations may require that a Diesel Particulate Filter (DPF) be included in the aftertreatment system to reduce the particulate emissions of the power system. A DPF is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. A diesel-powered engine equipped with a properly functioning DPF will emit no visible smoke from its exhaust. DPFs need to be accessible because they typically require periodic maintenance. For example, a method must exist to access, clean, and/or replace the filter. In contrast, if the power source uses natural gas as fuel, a particulate filter is not required, but an oxidation catalyst or other system might be. Access to these all devices is required for maintenance, replacements and upgrades.
Whenever the power source burns a hydrocarbon-based fuel, exhaust gases may need to be purified using an aftertreatment system incorporating technologies such as a Particulate Filter (PF), Oxidation Catalysts (OC) and/or Selective Catalytic Reduction (SCR). In OC and SCR devices, catalytic combustion is used to break down pollutants in the exhaust stream into innocuous components.
Additionally, diesel engines manufactured in the United States on or after Jan. 1, 2011 are required to meet lowered NOx levels. All of the United States heavy duty diesel engine manufacturers (manufacturing engines generating more than, for instance, 900 brake kilowatts) have presently chosen to utilize SCR aftertreatment to achieve these lower NOx standards. This Includes Caterpillar (C32 and 3500 series models), Cummins (QST and QSK), and MTU. These SCR-equipped engines require the continual addition of Diesel Exhaust Fluid (DEF), a urea solution, to enable the process.
SCR is a means of converting nitrogen oxides, also referred to as NOx, with the aid of a catalyst into diatomic nitrogen, N2, and water, H2O. A reductant, typically anhydrous ammonia, aqueous ammonia or urea, is added to a stream or flue of exhaust gas and is adsorbed onto a catalyst. Carbon dioxide (CO2) is a reaction bi-product when urea is used as the reductant. The NOx reduction reaction takes place as the gases pass through a catalyst chamber. Before entering the catalyst chamber, the ammonia, or other reductant (such as urea), is injected and mixed with the exhaust gases. SCR systems must have a mixing section of sufficient length to achieve high NOx reduction. SCR systems typically have numerous elements or components, including one or more reductant storage tanks, lines, valves, pumps, vaporizers, mixers, nozzles, injectors, ductwork, heat exchangers, air compressors, air heaters and fans, as well as control systems. External power may be required to operate many of these components of SCR systems. However, shore power is not always available for independent operation of the SCR system.
Aftertreatment systems, especially those incorporating SCR systems, are usually large in proportion to the corresponding engines, and in the past have fit only outside of the housings containing the power system. The sheer size and complexity of these aftertreatment systems has previously prevented them from being able to be mounted in the same container as the power system. Mounting aftertreatment systems externally to power system containers adds size and complexity to the combined systems, rendering them difficult and expensive to transport and set-up.
Another problem with present externally-mounted aftertreatment systems is that they cannot easily be modified to attach to different types of engines, generators or power equipment. An advantage of the modular features of the present power system is that various combinations of engines, generators and/or power equipment can be readily replaced or substituted for other combinations of engines, generators or power equipment with few or no changes to its aftertreatment system.
The typical process of attaching aftertreatment systems to power equipment involves mounting individual components of the aftertreatment system to the outside of the housing of the unit containing the equipment. Aftertreatment systems may include several functional elements that must be mounted and interconnected with each other. Consequently, individual contractors or support personnel must travel to the site where the power equipment is to be located, determine the proper location for the respective components of the aftertreatment system, prepare the exhaust for the attachment of the aftertreatment elements, mount each aftertreatment element, and connect the aftertreatment elements to each other and to the exhaust of the engine. A final test is then necessary to check the efficacy of the installation, make repairs as necessary and retest. This process is both time consuming and expensive.
When an aftertreatment system is to be added to a portable power system, additional difficulties arise. Portable power systems are sometimes referred to as power modules. The top sides of most power modules are not strong enough to support the weight of an aftertreatment system. Therefore, a typical procedure for attaching an aftertreatment system to a power module includes designing and installing support structure and framing to the housing of the power module. The aftertreatment elements are then attached to the support structure. Adding supporting members to the housing increases the time and expense required to install the aftertreatment system.
Transportation problems are also inherent in the current method of adding aftertreatment systems to the outside of power systems. Individual aftertreatment elements are not easily transported via typical shipping methods. In addition, when supporting members are added to the exteriors of housings of portable power systems, the supporting members add width and/or length to the housings. Therefore, these modified housings are often too large to be shipped via conventional means. In fact, special permits are often required to transport such modified housings on highways.
U.S. Pat. No. 4,992,669 issued to Parmley on Feb. 12, 1991 (the '669 patent) discloses a modular energy system in which a driven unit is connected to a driving unit via a shaft. These modular units are attached to each other via locking assemblies. However, the units that are shown in the '669 patent are each the same size. Stacking such units on top of each other could result in wind loads on the system of sufficient strength to cause damage to the system. In addition, the driven units in the '669 patent do not provide support for internal engine processes but merely use the power created by the driving units.
The present invention, which includes internally integrated aftertreatment elements, solves one or more of the problems set forth above.